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7.5 Mercury bogging

B

barelyfloats

New member
1973 7.5hp SN 348xxx bogging...

The first signs of an issue i could run about 2 mins at WOT and engine suddenly shut down (assume the cylinder shut down?). It would then take a few minutes to restart. i read all the online threads...tried a bunch of things to no avail: running gas from another can with hose straight in, cleaned fuel lines, make sure no leaks in fuel lines, new bulb. Still had issue...

Phase II of my efforts was rebuilding the carb, and changing to a new float. Starts first pull, runs fine at low speed, then a little surging and bogging starts above 1/2 speed, i can pull choke out a little and go to WOT and keep it running without shut down. Reading other threads lead me to believe issue is lower crank seal? ...If that is the case, any other wearout items worth replacing while i have it apart? Thanks in advance.
 
One of two things: Main jet is too lean (seen that on those), or insufficient fuel pressure. The fuel pumps on some of these motors were so weak, Merc themselves put out a bulletin on how to replace them with aftermarket [pumps. Done several of them.

Jeff
 
Thank you Jeff. I also want to cross off that I have my fuel pump / carb rebuild correct.

Mine is type "B" from Mercarb and it has the integral fuel pump, and I used the fiber check valve gasket/diaphragm, since that's what was in there before. SELOC manual did not specify fiber or rubber and both came in my kit...so i have an 'extra' check valve gasket in the pump kit? Illustration only shows one going in so let me know.

On type "F" Tillotsons, the manual does show "fiber" AND "rubber" check valve both being installed in a separate illustration page (see below). Note actual rebuild picture for type "F" only shows one check valve going into the pump and does not specify fiber or rubber. Confusing there too.

typeF.jpg

So back to me having the type B, what would you recommend? Fiber, Rubber or ...?
 
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